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This week's challenge.
One evening last week the Orange warning light came on with error messages ' Check Rear Lights' and 'Cruise Control Not Available'. The problem resolved on restarting and all messages cleared. No obvious faults with lights could be found. It was dark and cold so front and rear screen heaters were on, the car was in defrost mode and the heated seat was on. I put the problem down to a power glitch of some kind. Yesterday the Orange warning light came on with error message 'Check Rear Lights'. Again the fault cleared on restarting and the messages cleared. No obvious fault with lights. This time it was daylight and the electrics were not loaded. Today I had the Orange warning light with error messages 'Check Rear Lights' and 'Cruise Control Not Available' and again restarting the car resolved the issues and all messages cleared. This time in daylight, lights off.
Any suggestions?

Has the car been used regularly of late? Reason for the question is that at this time of year, these cars need every bit of help they can get from a really good battery. Before you get deep into having fault codes read, it might be worth having the battery checked first. Let us know how things turn out.
Ian

Hi Ian,
Yes. The car is in regular use. It's not wrapped up but is used every day. Certainly the battery should be topped up but maybe age is catching up with it..........
Rod

Rod

I assume all your lights are working ok.

If you have Cruise Control & have is switched on at the Central Console then it is probably the Brake Switch.

Easiest way to test without Code Reader etc. is to turn off the Cruise Control. You should not get any error messages. After a few trouble free days of driving turn on the Cruise Control Switch. After a while the Rear Light Message should re-appear. If you have set the Cruise Control to a speed (not just 'enabled' Cruise Control) at time of the error message you may get additional error messages regarding reduced power etc.

The Brake Switch has 2 micro switches (on Cruise Control fitted XK's). One for the Brake Switch & 2nd for the Cruise Control System.

If you intend to buy a replacement Brake Switch make sure you get the 4 wire one (2 micro switches)

If you are happy to de-solder & solder a new micro switch then this would be a cheaper option. If you are only replacing one switch you will need to test to determine which micro switch is for the Cruise Control. (I would recommend replacing both micro switches as they have had equal use!)

AllanJ

Additional info.

Foot Brake Switch

The Jaguar Part Numbers (for X100) are:
LJB6420AA - 2 wire for non Cruise Control
LJB6420BB - 4 wire for Cruise Control fitted XK's

The 2 units use the same plug & socket connector (4 'in line' pins) (Brake light uses the 2 outer pins & the Cruise Control uses the middle 2 pins) & you cannot read the part number off the unit when it's in place.

Regards

AllanJ

Hi Allan,

Thanks for the info. When the fault first appeared Cruise Control was inactive. Once the fault cleared itself Cruise operated OK but the second instance where the 'check rear lights' only came on fits your prediction that this would happen. I now understand that with a shared switch unit that the problems can be easily linked. I'll check this out.

Rod